The present invention relates to electronic equipment enclosures such as telecommunications repeater housings. More particularly, the invention relates to methods and systems of heat transfer for electronic enclosures.
Electronic cards such as telecommunications repeaters and other electronic equipment are often housed in enclosures that are required to bear the elements such as sun, rain, salt fog, pollution, heat as well as fire. These enclosures can also be subjected to partial or total submersion in water and arc required to be sealed against a pressure differential. These sealed enclosures are also required to remove energy, usually in the form of heat, generated by the electronic equipment in the enclosures. Many enclosures trap heat generated by the electronics. The build up of heat within these enclosures can cause significant problems for the electronic equipment by challenging the temperature limits of the electronic devices and causing device failure.
Often enclosures include card cages that collect and release heat into the enclosure environment and the heat becomes trapped. These card cages are typically single structures that continually exchange heat between the cards and the air within the enclosures without substantially moving the heat to the exterior of the enclosure. Because the card cage is one structure the structure becomes saturated with energy and can increase the heat build up within the enclosure.
The build up of heat within the enclosures can be further exasperated by enclosures that are made of materials having poor conductive properties. For many reasons such as weight, corrosion, and safety, telecommunications enclosures are often made of composites that have poor conductive properties. As a result composite enclosures severely limit the amount of heat transfer through the enclosure. Some applications provide a series of materials through which heat is transferred from the electronics devices to the ambient air. For example some electronic enclosures transfer heat from multiple electronic cards to a single card cage to a conductive liner which protrudes out through openings in the enclosure to one or more heat sinks. Other enclosures include a conductive cover and heat is conducted to the cover for dissipation to the ambient air.
Electronic devices are often lined up in rows and columns within card cages where the path from the inner cards to the ambient air is significantly longer than cards situated along an edge of the card cage. This causes significant heat build up for the inner cards. Further, good heat transfer requires consistent and preferably direct contact between transfer materials e.g. the repeater and card cage. It is difficult to get and keep the electronics cards in contact with the card cage. If good contact is not maintained poor heat transfer results and the rate of failure for the electronic devices is high. Some enclosures include active devices such as cams that require a technician or user to engage the device. The active devices force the electronic cards and card cage into contact but are prone to failure and are often overlooked by technicians and not engaged. Additionally, electronic cards come in many different styles and contact with heat transfer members do not take into consider open frame repeaters where the repeaters are encased in a box or frame with a portion of the sides removed.
Electronics cards are also susceptible to vibration and gravity. Cards are often retained in an enclosure only by an electrical connection such as insertion into an electrical socket. Due to vibration during shipping and operation the cards can become loose and dislodged from the electrical connectors. The cards can also be loosened when subjected to mounting locations that force the electronic cards to xe2x80x9changxe2x80x9d from the electrical socket. The use of active retention devices, such as cams, requires human intervention and is not reliable. Loose connections cause operation errors and result in time consuming and costly service calls.
Electronic equipment enclosures such as repeater housings are often heavy and cumbersome. The enclosures are difficult to carry and maneuver in small places such as mounting on telephone poles or into manhole compartments. Any enclosure which exceeds a set weight is required to be equipped with a lifting mechanism for attaching hoisting cables or chains. Often enclosures are lifted using one of the mounting feet attached to the exterior of the enclosure. The stress caused by the weight of the enclosure can lead to pull out of the mounting foot, damage to the mounting foot and/or structural damage to the enclosure.
The need for additional items such as conductive liners adds to the weight and cost of the enclosures. Some liners are over molded and fit tight within the enclosure and as a result introduce stress on the liners. The enclosure and the liner are made of different materials that expand and contract at different rates. This expansion and contraction causes potential stress of these components and may cause the mean time between failures of the equipment to decrease. Over molding large metal parts is a very difficult process because of the difference in material shrinkage and mold operator alignment introduce tool friction and wear issues. Further, the addition of a liner adds another layer to tolerance stacking when assembling the enclosure.
In addition, enclosures are subjected to costly replacement when the heat sinks or other exterior components are deteriorated by corrosion or otherwise damaged. Complete replacement is costly and time consuming often causing a drop in service for subscribers. Repeater enclosures are often pressurized to aid in protection from the elements. Proper sealing of the enclosures is always a concern. In some enclosures over molded liners have been used to provide a seal between the liner and the enclosure. The added weight of these liners adds to the difficulty in installation of the enclosures.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an improved enclosure for electronics equipment that overcomes the above noted imitations.
The above-mentioned problems with enclosures for electronics equipment and other problems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification.
An electronics enclosure is provided. The enclosure includes a modular card cage adapted to receive one or more electronic circuit cards and a heat sink adapted to protrude through an opening of an enclosure and couple to the modular card cage. The modular card cage and the heat sink provide an isolated heat transfer path for heat, produced by each of the one or more electronic circuit cards, to be removed from the enclosure.
In another embodiment, an electronics enclosure is provided. The enclosure includes one or more walls having at least one aperture, a plurality of modular card cages, wherein each card cage is adapted to receive one or more electronics cards; and a plurality of heat sinks. Each heat sink is adapted to protrude through one of the apertures and to couple to one of the plurality of modular card cages. Each aperture provides a direct path through which energy produced by the one or more electronics cards is removed from the enclosure.
In one embodiment, a heat transfer module is provided. The heat transfer module includes a modular card cage adapted to couple to one or more electronic circuit cards, an interface adapted to couple with the modular card cage, and heat sink integral with the interface. The heat transfer module provides isolated heat transfer paths from the one or more electronic circuit cards to the heat sink.
In one embodiment, a method for transferring heat from a circuit card is provided. The method comprises conducting heat from the circuit card to a card cage that is in contact with the circuit card and conducting the heat from the card cage to a heat sink. The heat sink is in contact with the card cage and extends through an aperture in a housing containing the card cage from an exterior to an interior of the housing. The heat sink is removably attached to the housing so as to seal the aperture against a pressure differential.